The present invention relates to a method and apparatus for plating and polishing a conductive material on a semiconductor substrate. More particularly, the present invention is directed to a method and apparatus for first plating and then polishing the conductive material on the semiconductor substrate using a single apparatus. Moreover, the present invention is directed to a method and apparatus for intermittently applying the conductive material to the semiconductor substrate and also intermittently polishing the substrate when such conductive material is not being applied to the substrate. Also, the present invention provides a method and apparatus that plates/deposits and/or polishes a conductive material on a substrate surface using a novel pad assembly.
A conventional process step in the manufacturing of integrated circuits and devices involves plating a metal layer on a semiconductor wafer surface using a plating apparatus. Typically, the wafer surface has been previously etched and contains many holes and/or trenches. One goal of wafer plating is to uniformly fill the holes and trenches with a conductive material. However, it is very difficult to uniformly fill the holes and trenches such that no voids exist. It is well known that the existence of the voids results in poor performance and defective devices. After such plating step, a polishing step is typically performed using a polishing apparatus to achieve a generally planar surface on the wafer.
Plating the wafer surface with the conductive material over a seed metal layer has important and broad application in the semiconductor industry. Traditionally, aluminum and other metals are plated as one of many metal layers that make up a semiconductor chip. However, in recent times, there is great interest in copper deposition for interconnects on semiconductor chips, because, compared to aluminum, copper reduces electrical resistance and allows semiconductor chips to run faster with less heat generation, resulting in a significant gain in chip capacity and efficiency. Furthermore, copper is known to be a better conductor than aluminum.
Thin film plating of copper into sub-micron holes and trenches is becoming more difficult in ULSI chip processing, particularly when the feature size is below 0.25 xcexcm with the aspect ratio greater than 5 to 1. Common chemical vapor deposition is being used to fill these holes and trenches etched into silicon substrates. Unfortunately, this process so far has yielded a very high cost for developing and integrating interconnects for ULSI technology.
Accordingly, a more accurate, cost effective, and reliable manner of applying a conductive material to the semiconductor substrate is needed.
It is an object of the present invention to provide a method and apparatus that plates/deposits a conductive material on a semiconductor workpiece surface and then polishes the same workpiece surface.
It is another object of the present invention to provide a method and apparatus that plates/deposits a conductive material on a workpiece surface using brush plating or electro chemical mechanical deposition and polishes the same workpiece surface using electropolishing or chemical mechanical polishing.
It is a further object of the present invention to provide a method and apparatus having multiple chambers in a single apparatus for plating/depositing the conductive material and polishing the workpiece surface.
It is yet another object of the present invention to provide a method and apparatus having novel pad assemblies for both plating/depositing the conductive material and polishing the workpiece surface.
It is yet another object of the present invention to provide a method and apparatus that plates/deposits a conductive material on a workpiece surface without a pad or other fixed feature making direct contact with the workpiece surface.
These and other object of the present invention are obtained by providing separate plating and polishing steps in close proximity of each other in a single apparatus. A first chamber may be used to plate/deposit the conductive material from an electrolyte solution to the workpiece surface. This is achieved by providing a pad mounted on a cylindrical anode and applying the conductive material to the workpiece surface using the electrolyte solution disposed on the pad, or through the pad.
An apparatus that performs such plating includes an anode and a cathode, a workpiece, or a workpiece that is spaced apart from the anode. A pad mounted on the cylindrical anode rotates about a first axis and the workpiece rotates about a second axis, and metal from the electrolyte solution is deposited on the workpiece when a potential difference is applied between the workpiece and the anode.
Alternatively, the plating chamber may include an anode plate spaced apart from the cathode or the workpiece. Upon application of power to the anode plate and the cathode, the electrolyte solution disposed in the plating chamber is used to deposit the conductive material on the workpiece surface.
In a polishing chamber, a pad is also mounted on another cylindrical anode or a cylindrical roller for polishing the workpiece surface. Polishing may be accomplished using either an electropolish or a chemical mechanical polishing method. The polishing of the workpiece surface preferably prevents accumulation of the conductive material to certain areas of the workpiece while providing a generally planar surface.
The present invention further describes novel anode assemblies having unique anode-pad arrangements that can be used to plate and/or polish the workpiece surface.